The present invention relates to a method and a device for removing spatter which has accumulated on a nozzle of an arc welding torch, and more particularly relates to such a method and a device for removing such accumulated spatter, in which the application of a sharp electromagnetic force detaches the spatter from said arc welding torch nozzle and removes it away therefrom. Particularly, the present invention is applicable to the removal of spatter from the interior cylindrical surface of the tip portion of the nozzle of an arc welding torch which is used for so called gas shielded welding.
Nowadays various arc welding processes are often employed, and in these the tip of a welding wire or rod is approached near to an article or articles to be welded, and an arc is set up between said welding rod tip and said article or articles to be welded, so as locally to raise up the temperature of the part or parts to be welded so that they locally melt. In particular, arc welding processes employing a flow of a so called shield gas, i.e. of a gas which is inert and which particularly does not contain any substantial amount of free oxygen, are frequently used for welding articles made of a metal or metals which are liable to be deleteriously oxidized if such a gas shield is not utilized. And in such a process typically a nozzle is provided around the aforesaid tip of the welding rod where the welding process is actually occurring, so as to direct and channel the flow of the shield gas in an appropriate manner.
A concrete example of such a construction is shown in longitudinal sectional view in FIG. 1 of the accompanying drawings: in this figure, which generally relates to the present invention but in which the shown arc welding torch (which itself does not incorporate the present invention) is of a per se known and prior art type, the reference numeral 1 denotes a tubular tip portion of a nozzle denoted as a whole as 10 of an arc welding torch, and the main body 2 of this arc welding torch, to which said tubular nozzle tip portion 1 is threadingly fitted, is formed with an internal cavity in which a tubular welding rod holder 4 is provided. This tubular welding rod holder 4 has a contact tip portion 3 at its extreme end located just within the open end portion of the tubular nozzle tip portion 1, and in a tubular hole formed through said tubular welding rod holder 4 and said contact tip portion 3 there is slidably fitted a welding rod 5 with its end portion projecting out from the contact tip portion 3 and the tubular nozzle tip portion 1. As the welding process is conducted in a per se known manner, the welding rod 5 is steadily consumed by the arc which is set up between the tip portion of said welding rod 5 and the work piece or pieces, and accordingly more of said welding rod 5 is continuously fed through the contact tip portion 3 from the tubular welding rod holder 4 from a source not particularly shown in the figure. Meanwhile, during the welding process, a flow 9 of so called shield gas, which should be an inert gas particularly not containing any substantial quantity of free oxygen, is introduced through a hole 8 into the inside of this welding torch nozzle 10, i.e. into the interior portions of the body 2 of the welding torch and of the tubular nozzle tip portion 1, around the contact tip portion 3 and the tubular welding rod holder 4 housed therein, and this shield gas flow 9 flows out of the open end of the tubular nozzle tip portion 1, around the end of the welding rod 5 at which the welding process is being conducted. Thereby the molten metal portions involved in the welding process, and the welding arc, are shielded from the oxygen in the atmosphere, and said molten metal portions are prevented from degradation, thus improving the efficiency of welding action.
However, a problem conventionally arises with the use of such a type of welding torch and nozzle, as follows. As the welding process is conducted, molten metal droplets from the molten metal portions involved in the welding process are expelled from said portions, and strike against, particularly, the interior portions of the tubular nozzle tip portion 1, i.e. against the extreme tip portions of the inner cylindrical surface of said tubular nozzle tip portion 1, and then solidify and adhere there as spatter deposits such as those which are denoted in FIG. 1 by the reference numeral 6. As a result of this process, after substantial building up of such spatter deposits 6, the flow of the shield gas flow 9 through said tubular nozzle tip portion 1 becomes uneven and is disturbed, and as a consequence the shielding capability of said shield gas flow 9 is deteriorated, and atmospheric air comes to be able to reach the molten metal portons involved in the welding process and the welding arc itself. As a result, air holes such as so called blow holes are liable to be generated in the welded portions of the work, and the mechanical strength and other properties of the weld are liable to be deteriorated.
Conventionally, in order to prevent these problems, such spatter deposits 6 have been removed by the use of a brush or the like; such a concept is disclosed, for example, in Japanese Patent Application Laying Open Publication Ser. No. 59-73186 (1984), which it is notintended hereby to admit as prior art to the present patent application except to the extent in any case mandated by applicable law. However, since the tubular nozzle tip portion 1 is normally made of metal, the accumulation of the spatter deposits 6 is accordingly fairly rapid, and therefore such removal work must necessarily be performed relatively frequently, which causes problems of increased labor requirements and reduced efficiency of utilization of manufacturing facilities. Further, repeated brushing of the tubular nozzle tip portion 1 is liable to deteriorate it.
Another approach to prevention of these problems, is to remove such spatter deposits 6 by the use of a spatter removal device equipped with a rotary blade, in a so called scraping process; such a concept is disclosed, for example, in Japanese Utility Model Application Laying Open Publication Ser. No. 58-47381 (1983), which also it is not intended hereby to admit as prior art to the present patent application except to the extent in any case mandated by applicable law. However, in such a case, such repeated scraping of the tubular nozzle tip portion 1 is even more liable to damage or to deteriorate it.
Yet another approach to prevention of these problems is for the tubular nozzle tip portion 1 to be made out of a ceramic material; such a concept is disclosed, for example, in Japanese Utility Model Application Laying Open Publication Ser. No. 48-12323 (1973), which also it is not intended hereby to admit as prior art to the present patent application except to the extent in any case mandated by applicable law. However, in such a case, although the deposition of the spatter deposits 6 is reduced, it still occurs to some extent, and accordingly the work of spatter deposit removal is still required. Further, such a ceramic nozzle is even more liable to damage such as cracking during such spatter deposit removal.
Another problem attendant upon such spatter deposit removal is that, if the removal of the spatter deposits 6 is attempted immediately after the welding process, the temperature of the tubular nozzle tip portion 1 may be so high that the operator may burn himself or herself. This problem is accentuated with the use of a ceramic nozzle, which has a lower coefficient of thermal conductivity and accordingly takes longer to cool down.
Yet another problem attendant upon such spatter deposit removal is that, during the removal of the spatter deposits 6, it is quite likely that the tubular nozzle tip portion 1 may become scratched. Again, this problem is accentuated with the use of a ceramic nozzle, which by its nature is more easily damaged. if such scratching should occur, not only will the tubular nozzle tip portion 1 become more prone to the accumulation of spatter deposits 6 in the future, but it may be weakened and become subject to subsequent cracking.